Electronic flat panel displays have achieved considerable commercial success in the last decade in vehicular instrumentation as well as in office and factory equipment and in other applications. In vehicles for example, such information displays may provide fuel, temperature and pressure information with seven segment digit displays composed of active LED (light emitting diodes) or LCD elements and/or with an LED or LCD (liquid crystal display) bar graph. Engine speed and vehicle speed information is another example.
These flat panel displays are generally divided into groups, those which are self-illuminated and those which are not, e.g. an LED display is self-illuminating and an LCD display is not. The problem confronting the display system manufacturer, and these manufacturers in large part are not the manufacturers of active display elements, is to combine additional graphics such as symbols and word information with the active elements and to illuminate them adequately in a relatively low-cost manner. Fixed graphics such as by printing applied to the forward surface of these active elements and the non-self illuminating active elements must be illuminated. Light sources that provide this illumination create reflection problems and in spite of extensive efforts have not provided adequate.
Edge-lighted graphic elements are broadly known in the prior art, such as shown in the Swatten U.S. Pat. No. 4,247,747 in which a flexible plastic sheet carrying numeric switch indicia covers a flexible contact switch with a plurality of switches each under one of the switch numbers on the flexible transparent sheet. In the Swatten patent there are no active display elements and the graphics may be printed on either the front or the rear sheet of the flexible transparent sheet, and further the sheet itself is thin and flexible and spaced too far from a backing sheet to adequately illuminate the graphics thereon.
It is the primary object of the present invention to ameliorate the problems noted above in active and passive informational graphic display combinations.